Biological Evaluation of Naproxen–Dehydrodipeptide Conjugates with Self-Hydrogelation Capacity as Dual LOX/COX Inhibitors

Abstract

The use of peptide–drug conjugates is emerging as a powerful strategy for targeted drug delivery. Previously, we have found that peptides conjugated to a non-steroidal anti-inflammatory drug (NSAID), more specifically naproxen–dehydrodipeptide conjugates, readily form nanostructured fibrilar supramolecular hydrogels. These hydrogels were revealed as efficacious nano-carriers for drug delivery applications. Moreover, the incorporation of superparamagnetic iron oxide nanoparticles (SPIONs) rendered the hydrogels responsive to external magnetic fields, undergoing gel-to-solution phase transition upon remote magnetic excitation. Thus, magnetic dehydrodipeptide-based hydrogels may find interesting applications as responsive Magnetic Resonance Imaging (MRI) contrast agents and for magnetic hyperthermia-triggered drug-release applications. Supramolecular hydrogels where the hydrogelator molecule is endowed with intrinsic pharmacological properties can potentially fulfill a dual function in drug delivery systems as (passive) nanocariers for incorporated drugs and as active drugs themselves. In this present study, we investigated the pharmacological activities of a panel of naproxen–dehydrodipeptide conjugates, previously studied for their hydrogelation ability and as nanocarriers for drug-delivery applications. A focused library of dehydrodipeptides, containing N-terminal canonical amino acids (Phe, Tyr, Trp, Ala, Asp, Lys, Met) N-capped with naproxen and linked to a C-terminal dehydroaminoacid (ΔPhe, ΔAbu), were evaluated for their anti-inflammatory and anti-cancer activities, as well as for their cytotoxicity to non-cancer cells, using a variety of enzymatic and cellular assays. All compounds except one were able to significantly inhibit lipoxygenase (LOX) enzyme at a similar level to naproxen. One of the compounds 4 was able to inhibit the cyclooxygenase-2 (COX-2) to a greater extent than naproxen, without inhibiting cyclooxygenase-1 (COX-1), and therefore is a potential lead in the search for selective COX-2 inhibitors. This hydrogelator is a potential candidate for dual COX/LOX inhibition as an optimised strategy for treating inflammatory conditions.

Dehydropeptide Supramolecular Hydrogels and Nanostructures as Potential Peptidomimetic Biomedical Materials

“…The increased proteolytic resistance of these naproxen-dehydropeptides, compared with naproxen-dipeptides consisting of canonical amino acids, could potentially affect their ability to release naproxen and act as anti-inflammatory prodrugs. Moreira et al considered that these conjugates may themselves retain the anti-inflammatory properties of the conjugated NSAID and therefore be suitable as hydrogels for “self-delivery” [ 79 ]. With this in mind, the biological activities of a panel of hydrogelator naproxen conjugates was assessed.…”

“…The inhibition of proteasome enzymes is reported to have potential in cancer therapy. A conjugate that can both bind COX enzymes and inhibit proteasome enzymes may be a powerful combination for targeting cancer cells [ 79 ].…”

Evaluation of a Model Photo-Caged Dehydropeptide as a Stimuli-Responsive Supramolecular Hydrogel

“…The peptide capping groups are usually bi- or tricyclic aromatic groups, such as fluorenylmethoxycarbonyl (Fmoc), 9-anthracenemethoxycarbonyl (Amoc), indole-3-acetyl, naphthoyl or naproxen [ 11 ]. In our laboratory, we have found that various dehydrodipeptides capped on the N -terminus with either naproxen (an NSAID drug) or a carboxybenzyl (Cbz or Z) group (e.g., 1a – d , Figure 1 A), are capable of forming stable hydrogels at concentrations as low as 0.1% [ 12 , 13 , 14 , 15 , 16 , 17 ]. The presence of the dehydroamino acid residue provides proteolytic resistance and greater conformational rigidity [ 13 , 14 , 15 , 16 , 17 ].…”

“…Although based on a similar principle, this hydrogel system has some key differences to the systems described by Hamachi [ 29 ] and Adler-Abramovich [ 18 ]. Firstly, both the putative hydrogelator, CNB-Phe-ΔPhe-OH ( 2 ), and its UV-deprotection product, H-Phe-ΔPhe-OH ( 3 ), are expected to be resistant to action of endogenous peptidases [ 13 , 14 , 15 , 16 , 17 , 41 , 42 ]. Both our own group, and the group of Chauhan, have demonstrated the stability of the -Phe-ΔPhe- motif compared to the canonical dipeptide—-Phe-Phe- motif [ 41 ].…”

“…Both our own group, and the group of Chauhan, have demonstrated the stability of the -Phe-ΔPhe- motif compared to the canonical dipeptide—-Phe-Phe- motif [ 41 ]. In the wider scope, this increased enzymatic stability would also be present in modified systems involving the uncaging of biologically active dehydrodipeptides ( Figure 1 D) [ 13 , 14 , 15 , 16 , 17 , 41 , 42 ]. Secondly, the UV-deprotection compound in this case is H-Phe-ΔPhe-OH ( 3 ), which, rather unusually for a dipeptide lacking a capping group, is already known to be a hydrogelator under certain conditions, as are some other uncapped dehydropeptides [ 41 , 42 ].…”